Volume 50: 25-35, 2001

 

Metabolism of Branched-Chain Amino Acids in Starved Rats: The Role of Hepatic Tissue

M. HOLEČEK, L. ŠPRONGL1, I. TILŠER2

Department of Physiology, Faculty of Medicine, Charles University, Hradec Králové, 1University Hospital Motol, Prague,
2Department of Pharmacology, School of Pharmacy, Hradec Králové, Czech Republic

Received February 15, 2000
Accepted May 16, 2000


Summary
Parameters of branched-chain amino acids (BCAA; leucine, isoleucine and valine) and protein metabolism were evaluated using L-[1-14C]leucine and a-keto[1-14C]isocaproate (KIC) in the whole body and in isolated perfused liver (IPL) of rats fed ad libitum or starved for 3 days. Starvation caused a significant increase in plasma BCAA levels and a decrease in leucine appearance from proteolysis, leucine incorporation into body proteins, leucine oxidation, leucine-oxidized fraction, and leucine clearance. Protein synthesis decreased significantly in skeletal muscle and the liver. There were no significant differences in leucine and KIC oxidation by IPL. In starved animals, a significant increase in net release of BCAA and tyrosine by IPL was observed, while the effect on other amino acids was non-significant. We conclude that the protein-sparing phase of uncomplicated starvation is associated with decreased whole-body proteolysis, protein synthesis, branched-chain amino acid (BCAA) oxidation, and BCAA clearance. The increase in plasma BCAA levels in starved animals results in part from decreased BCAA catabolism, particularly in heart and skeletal muscles, and from a net release of BCAA by the hepatic tissue.


Key words
Nutrition · Starvation · Leucine · Protein Metabolism · Branched-chain amino acids

Reprint requests
Dr. Milan Holeček, Department of Physiology, Charles University, Faculty of Medicine, Šimkova 870, 500 01 Hradec Králové, Czech Republic, fax +420-49-5210190, e-mail:
holecek@lfhk.cuni.cz

 

PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology, Czech Academy of Sciences

ISSN 0862 - 8408

Issue 1